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Title: Role of the Hydrophobic Bridge in the Carbapenemase Activity of Class D β-Lactamases

Class D carbapenemases are enzymes of the utmost clinical importance due to their ability to confer resistance to the last-resort carbapenem antibiotics. We investigated the role of the conserved hydrophobic bridge in the carbapenemase activity of OXA-23, the major carbapenemase of the important pathogen Acinetobacter baumannii. We show that substitution of the bridge residue Phe110 affects resistance to meropenem and doripenem and has little effect on MICs of imipenem. The opposite effect was observed upon substitution of the other bridge residue Met221. Complete disruption of the bridge by the F110A/M221A substitution resulted in a significant loss of affinity for doripenem and meropenem and to a lesser extent for imipenem, which is reflected in the reduced MICs of these antibiotics. In the wild-type OXA-23, the pyrrolidine ring of the meropenem tail forms a hydrophobic interaction with Phe110 of the bridge. Similar interactions would ensue with ring-containing doripenem but not with imipenem, which lacks this ring. Our structural studies showed that this interaction with the meropenem tail is missing in the F110A/M221A mutant. These data explain why disruption of the interaction between the enzyme and the carbapenem substrate impacts the affinity and MICs of meropenem and doripenem to a larger degree thanmore » those of imipenem. Our structures also show that the bridge directs the acylated carbapenem into a specific tautomeric conformation. Furthermore, it is not this conformation but rather the stabilizing interaction between the tail of the antibiotic and the hydrophobic bridge that contributes to the carbapenemase activity of class D β-lactamases.« less
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [1]
  1. Univ. of Notre Dame, Notre Dame, IN (United States)
  2. Stanford Univ., Menlo Park, CA (United States)
  3. Univ. of Notre Dame, Notre Dame, IN (United States); Decisions Resource Group, Boston, MA (United States)
Publication Date:
Grant/Contract Number:
AC02-76SF00515; R01AI114668
Type:
Accepted Manuscript
Journal Name:
Antimicrobial Agents and Chemotherapy
Additional Journal Information:
Journal Volume: 63; Journal Issue: 2; Journal ID: ISSN 0066-4804
Publisher:
American Society for Microbiology
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; antibiotic resistance; β-lactamases; mechanisms of resistance
OSTI Identifier:
1503400

Stewart, Nichole K., Smith, Clyde A., Antunes, Nuno T., Toth, Marta, and Vakulenko, Sergei B.. Role of the Hydrophobic Bridge in the Carbapenemase Activity of Class D β-Lactamases. United States: N. p., Web. doi:10.1128/aac.02191-18.
Stewart, Nichole K., Smith, Clyde A., Antunes, Nuno T., Toth, Marta, & Vakulenko, Sergei B.. Role of the Hydrophobic Bridge in the Carbapenemase Activity of Class D β-Lactamases. United States. doi:10.1128/aac.02191-18.
Stewart, Nichole K., Smith, Clyde A., Antunes, Nuno T., Toth, Marta, and Vakulenko, Sergei B.. 2019. "Role of the Hydrophobic Bridge in the Carbapenemase Activity of Class D β-Lactamases". United States. doi:10.1128/aac.02191-18.
@article{osti_1503400,
title = {Role of the Hydrophobic Bridge in the Carbapenemase Activity of Class D β-Lactamases},
author = {Stewart, Nichole K. and Smith, Clyde A. and Antunes, Nuno T. and Toth, Marta and Vakulenko, Sergei B.},
abstractNote = {Class D carbapenemases are enzymes of the utmost clinical importance due to their ability to confer resistance to the last-resort carbapenem antibiotics. We investigated the role of the conserved hydrophobic bridge in the carbapenemase activity of OXA-23, the major carbapenemase of the important pathogen Acinetobacter baumannii. We show that substitution of the bridge residue Phe110 affects resistance to meropenem and doripenem and has little effect on MICs of imipenem. The opposite effect was observed upon substitution of the other bridge residue Met221. Complete disruption of the bridge by the F110A/M221A substitution resulted in a significant loss of affinity for doripenem and meropenem and to a lesser extent for imipenem, which is reflected in the reduced MICs of these antibiotics. In the wild-type OXA-23, the pyrrolidine ring of the meropenem tail forms a hydrophobic interaction with Phe110 of the bridge. Similar interactions would ensue with ring-containing doripenem but not with imipenem, which lacks this ring. Our structural studies showed that this interaction with the meropenem tail is missing in the F110A/M221A mutant. These data explain why disruption of the interaction between the enzyme and the carbapenem substrate impacts the affinity and MICs of meropenem and doripenem to a larger degree than those of imipenem. Our structures also show that the bridge directs the acylated carbapenem into a specific tautomeric conformation. Furthermore, it is not this conformation but rather the stabilizing interaction between the tail of the antibiotic and the hydrophobic bridge that contributes to the carbapenemase activity of class D β-lactamases.},
doi = {10.1128/aac.02191-18},
journal = {Antimicrobial Agents and Chemotherapy},
number = 2,
volume = 63,
place = {United States},
year = {2019},
month = {1}
}

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